Question

Ruby bought a watermelon weighing 5kg 200g. Out of this she gave 2kg 750g to her neighbor. What is the weight of the watermelon left with Ruby?

Answer 1

Hint: This question involves a simple concept of unit conversion and substitution. We know that all algorithmic processes can be done only between the same units. So, we have to convert both the quantities in the same unit, here we will convert all the units into grams and then solve further. After finding the weight of the watermelon Ruby had and that she gave to her neighbor, we will subtract those values, to get the weight of the watermelon left with Ruby. Here, we will use the unit conversion, 1kg = 1000g.

Complete step by step answer:
Now, we have been given the question that Ruby bought a watermelon weighing 5kg 200g. So, we will first convert this weight fully in terms of grams.
We know that 1kg = 1000g
So, we can write, $5kg=5\times 1000g=5000g$.
So, the weight of the watermelon which Ruby bought will be
= 5kg + 200g
= 5000g + 200g
= 5200g
Now, the weight of the watermelon she gave to her neighbor is 2kg 750g.
So, we will convert this weight also into grams. So, as we know that 1kg = 1000g, we can write, $2kg=2\times 1000=2000g$.
So, the weight of the watermelon that she gave to her neighbor will be,
= 2kg + 750g
= 2000g + 750g
= 2750g
Therefore, the weight of the watermelon left with Ruby can be found out as,
Weight of the watermelon she had – weight of the watermelon she gave to neighbor
= 5200g – 2750g
= 2450g
Now, we know that 1000g = 1kg, so we can write,
$1g=\dfrac{1}{1000}kg$
So, we can write 2450g as,
$\begin{align}
  & 2450g=\dfrac{1}{1000}\times 2450=\dfrac{2450}{1000} \\
 & =2.45kg \\
\end{align}$
Now, 2.45kg can be further written as,
2kg + 450g
= 2kg 450g

Therefore, we get that the weight of the watermelon left with Ruby is equal to 2kg 450g.

Note: We can convert the total weight in kg also and then subtract both the weights.
We know that $1g=\dfrac{1}{1000}kg$. So, we can write 5kg 200g as 5kg + 0.200kg = 5.2kg.
And we can write 2kg 750g as 2kg + 0.750kg = 2.75kg.
So, we will get the weight of the watermelon left as 5.2kg – 2.75kg = 2.450kg.
So, we can further write it as,
= 2kg + 0.450kg
= 2kg + 450g
= 2kg 450g
Hence, we get the same answer.